In this class, the following terms are used with the meanings indicated: "fibre" means a relatively-short, elongated member of natural or artificial material; "filament" means an endless or quasi-endless, elongated member of natural or artificial material; "yarn" means a unitary assembly of fibres, usually produced by spinning; "thread" means an assembly of yarns or filaments, usually produced by twisting. Attention is drawn to the Note following the title of class . Processes using enzymes or micro-organisms in order to: liberate, separate or purify a pre-existing compound or composition, or to treat textiles or clean solid surfaces of materials are further classified in subclass .